Mobile terminals, such as mobile phones or PDAs (Personal Digital Assistants), are driven by a rechargeable battery according to their features, and, in order to charge the battery, electrical energy is supplied to the battery of the mobile terminal by a separate charging device. Typically, the charging device and the battery have separate contact terminals, respectively, which allows the charging device and the battery to be electrically connected to each other by bringing the charging device into contact with the battery.
Since the contact terminals are exposed to the outside in the contact type of charging, the terminals are easily contaminated by foreign materials, which may cause a malfunction in the battery charging. In addition, in the case where the contact terminals are exposed to moisture, the charging may not be conducted correctly.
Recently, in order to solve the problems above, wireless charging technology (also called non-contact charging technology) has been developed and widely utilized in various electronic devices.
Wireless charging technology provides a system that uses wireless power transmission and reception in which, for example, the battery of a mobile phone may be automatically charged by simply placing the mobile phone on a charging pad without connecting to a separate charging connector. In general, wireless charging technology is well known to the public in other applications such as for charging wireless electric toothbrushes or wireless electric shavers. Wireless charging technology can enhance a device's waterproof function by eliminating the need for exposed terminals on the device for wired charging. Portability of the device is also improved since a wired charger is unnecessary to transport. Related technology is also expected to rapidly advance in the coming electric vehicle era.
Wireless charging technology generally uses an electromagnetic induction method using coils, a resonance method, and/or a radio wave radiation (RF/Microwave radiation) method in which electrical energy is converted into microwaves to be transmitted.